The present invention is directed to an apparatus for rotating a shaft or crankshaft. More particularly, the present invention is directed to an apparatus for precisely rotating a shaft or crankshaft, such as the crankshaft of an internal combustion engine, to one or more desired angular positions.
It is well known that internal combustion engines require the setting of various valve train components during their assembly. For example, it is typically necessary to set valve tappet clearance to ensure proper engine operation.
Whether in regard to the setting of valve tappet clearance or another valve train adjustment/setting operation, it is generally required to precisely rotate the crankshaft of such an engine in order to properly position the valve train component(s) of interest. Currently, such crankshaft rotation is typically accomplished manually, such as by an operator using a long-handled wrench adapted to engage an exposed portion of the crankshaft.
Obviously, manual rotation of an engine crankshaft is undesirable at least for ergonomic reasons, among others. In addition, it should be realized that an internal combustion engine typically has multiple cylinders, each having two or more valves. Hence, a task such as setting valve tappet clearance, for example, requires that the crankshaft of each engine be rotated numerous times throughout the overall process. It should also be realized that the crankshaft must be rotated precisely to a particular position so as to properly set the initial position of a valve train component(s) to be adjusted. This is typically accomplished during manual crankshaft rotation by rotating the crankshaft to a position that coincides with a particular marking appearing on a gauge or other alignment device. Clearly, the positioning accuracy of such a technique is limited.
The above problems are further complicated by the fact that modern internal combustion engines are being increasingly manufactured to tighter tolerances. Consequently, the clearances between valve train components (e.g., piston rings and cylinder walls) have been reduced, thereby leading to an increased resistance to crankshaft rotation. As such, manual rotation of an engine crankshaft is also becoming more difficult.
Therefore, it can be understood that what is needed is an apparatus and method for producing a precise and nonhuman powered rotation of a crankshaft. The present invention provides just such a result.